1. Field of the Invention
The present invention relates to an electrostatically powder coating method and an apparatus therefor, in which a gun for electrostatically powder coating is directed to an object to be coated, a DC electric field is formed in an area including the gun and the object to be coated so that a powder coating material jetted into the DC electric field is transferred and applied onto the object to be coated, and the object is then heated so that the applied coating material is baked on the object.
2. Description of Prior Art
Conventionally, electrostatic powder coating has been performed through the steps of; providing a gun for electrostatically powder coating separated from and directed to an object to be coated; jetting a powder coating material suspending in air from the gun with the simultaneous application of a DC high voltage onto the discharge nozzle of the gun to generate corona discharge; electrically charging the powder coating material by an ionic current from the gun to the object to be coated so that the charged powder coating material is transferred onto the surface of the object to be coated by Coulomb attraction to form a layer of the applied powder coating material thereon; and then heating the object so as to form a film of the powder coating material baked on the surface of the object.
In this case there has been such a disadvantage that the thickness of the powder coating material applied on the surface of the object to be coated varies with the position depending on the intensity of the electric field at the respective position, that is, depending on the shape and position of the object to be coated, so that it is difficult to apply the coating material with a uniform thickness, and that depending on the shape of the object to be coated a Faraday cylinder effect makes the so-called creeping and penetrating properties poor to thereby lower the efficiency in coating.